Synthesis and Evaluation of Artemisinin-Based Hybrid and Dimer Derivatives as Antimelanoma Agents

Searching for the Holy Grail - Highly Potent Bridged Endoperoxides for Targeted Cancer Therapy

The International Agency for Research on Cancer (IARC) recently estimated the global cancer burden in 2050. The statistics are startling, with a 77% hike and 35 million new cancer cases per year. The present discoveries have recommended plant-derived bridged endoperoxides or artemisinin-based semisynthetic analogues as safe, well-tolerated and powerful substitutes that could be effectively utilized as a warhead to fight against global enemies like cancer. In addition, artemisinin-based drug repositioning crucially can reduce overriding drug development expenditures and establish accessibility of approved drugs with low risk to patients. Hence, the present review article provides a comprehensive account of the recent chemical and synthetic advancement of diverse cytotoxic artemisinin derivatives such as C(10)-O, C, N, S linked artemisinin analogues, artemisinin-derived metal complexes, artemisinin-derived hybrids/conjugates with other pharmaceutically active substances, and artemisinin-derived dimers, trimers and tetramers perceived during the last three decades (1997-2024). Moreover, the current preclinical and clinical anticancer application prospects of artemisinin derivatives with other defined drugs and their utilization in combination therapy and also nanoformulation approaches for targeted drug delivery have been discussed.

The Antiviral and Antimalarial Prodrug Artemisinin from the Artemisia Species: A Review

Artemisinin is a truly fascinating drug in many ways. Since the unrestrained procedure of its detection, as an antimalarial drug, artemisinin has received a great deal of consideration. Recently, application of artemisinin-based combination therapy has been broadly applied for treating numerous ailments. Moreover, as an antimalarial compound, artemisinin and its associated compounds have abundant healing efficacy and can be repurposed for additional symptoms, like autoimmune infections, cancer, and viral contaminations. Recently a number of studies have highlighted the significance of the artemisinin-related compounds in SARS-CoV-2 treatment. The current review purposes to present a concise account of the history of the antiviral and antimalarial prodrugs-Artemisinin, from the Artemisia species. It is followed by its antiviral, antimalarial prospective, chemical nature and extraction procedure, photochemistry, mechanism of action, and its clinical trials and patents, and accentuates the significance of the mechanistic studies concerned for therapeutic results, both in viral and malarial circumstances.

Modulation of the Antimelanoma Activity Imparted to Artemisinin Hybrids by the Monoterpene Counterpart

Molecular hybridization is a widely used strategy in drug discovery and development processes that consists of the combination of two bioactive compounds toward a novel entity. In the current study, two libraries of hybrid derivatives coming from the linkage of sesquiterpene counterparts dihydroartemisinin and artesunic acid, with a series of monoterpenes, were synthesized and evaluated by cell viability assay on primary and metastatic melanoma cell lines. Almost all the obtained compounds showed micromolar antimelanoma activity and selectivity toward the metastatic form of this cancer. Four hybrid derivatives containing perillyl alcohol, citronellol, and nerol as monoterpene counterpart emerged as the best compounds of the series, with nerol being active in combination with both sesquiterpenes, dihydroartemisinin and artesunic acid. Preliminary studies on the mechanism of action have shown the dependence of the pharmacological activity of newly synthesized hybrids on the formation of carbon- and oxygen-centered radical species. This study demonstrated the positive modulation of the pharmacodynamic effect of artemisinin semisynthetic derivatives dihydroartemisinin and artesunic acid due to the hybridization with monoterpene counterparts.

Engineered Artesunate-Naphthalimide Hybrid Dual Drug for Synergistic Multimodal Therapy against Experimental Murine Lymphoma

Lymphoma can effectively be treated with a chemotherapy regimen that is associated with adverse side effects due to increasing drug resistance, so there is an emergent need for alternative small-molecule inhibitors to overcome the resistance that occurs in lymphoma management and overall increase the prognosis rate. A new series of substituted naphthalimide moieties conjugated via ester and amide linkages with artesunate were designed, synthesized, and characterized. In addition to the conjugates, to further achieve a theranostic molecule, FITC was incorporated via a multistep synthesis process. DNA binding studies of these selected derivatives by ultraviolet-visible (UV-vis), fluorescence spectroscopy, intercalating dye (EtBr, acridine orange)-DNA competitive assay, and minor groove binding dye Hoechst 33342-DNA competitive assay suggested that the synthesized novel molecules intercalated between the two strands of DNA due to its naphthalimide moiety and its counterpart artesunate binds with the minor groove of DNA. Napthalimide-artesunate conjugates inhibit the growth of lymphoma and induce apoptosis, including ready incorporation and reduction in cell viability. The remodeled drug has a significant tumoricidal effect against solid DL tumors developed in BALB/c mice in a dose-dependent manner. The novel drug appears to inhibit metastasis and increase the survival of the treated animals compared with untreated littermates.

Molecular Hybridization as a Strategy for Developing Artemisinin-Derived Anticancer Candidates

Artemisinin is a natural compound extracted from Artemisia species belonging to the Asteraceae family. Currently, artemisinin and its derivatives are considered among the most significant small-molecule antimalarial drugs. Artemisinin and its derivatives have also been shown to possess selective anticancer properties, however, there are several limitations and gaps in knowledge that retard their repurposing as effective anticancer agents. Hybridization resulting from a covalent combination of artemisinin with one or more active pharmacophores has emerged as a promising approach to overcome several issues. The variety of hybridization partners allows improvement in artemisinin activity by tuning the ability of conjugated artemisinin to interact with various molecule targets involved in multiple biological pathways. This review highlights the current scenario of artemisinin-derived hybrids with potential anticancer activity. The synthetic approaches to achieve the corresponding hybrids and the structure-activity relationships are discussed to facilitate further rational design of more effective candidates.

Acidity-Triggered Charge-Convertible Conjugated Polymer for Dihydroartemisinin Delivery and Tumor-Specific Chemo-Photothermal Therapy

Since the nonspecificity and nonselectivity of traditional treatment models lead to the difficulty of cancer treatment, nanobased strategies are needed to fill in the gaps of current approaches. Herein, a tumor microenvironment (TME)-responsive chemo-photothermal treatment model was developed based on dihydroartemisinin (DHA)-loaded conjugated polymers (DHA@PLGA-PANI). The synthesized DHA@PLGA-PANI exhibited enhanced photothermal properties under mild-acidic conditions and thus triggered local heat at the tumor site. Meanwhile, these iron-doped conjugated polymers of PLGA-PANI were used as the source of Fe, and benefiting from the Fe-dependent cytotoxicity of DHA, the burst of free radicals could be generated in tumors. Therefore, the combination of TME-responsive chemo-photothermal therapy could achieve effective tumor efficacy.

Synthesis of Artesunic Acid-Coumarin Hybrids as Potential Antimelanoma Agents

Current therapy against melanoma relies on surgical treatment or, in alternative, on conventional drug therapy. Often these therapeutic agents are ineffective due to the development of resistance phenomena. For this purpose, chemical hybridization emerged as an effective strategy to overcome the development of drug resistance. In this study, a series of molecular hybrids were synthesized combining the sesquiterpene artesunic acid with a panel of phytochemical coumarins. Cytotoxicity, antimelanoma effect, and cancer selectivity of the novel compounds were evaluated by MTT assay on primary and metastatic cells and on healthy fibroblasts as a reference. The two most active compounds showed lower cytotoxicity and higher activity against metastatic melanoma than paclitaxel and artesunic acid. Further tests, including cellular proliferation, apoptosis, confocal microscopy, and MTT analyses in the presence of an iron chelating agent, were conducted with the aim of tentatively addressing the mode of action and the pharmacokinetic profile of selected compounds.

A comprehensive overview of Artemisinin and its derivatives as anticancer agents

Artemisinin is the crucial ingredient of artemisia annua, a traditional Chinese medicine used for the therapy of malaria in China for hundreds of years. In recent years, the anticancer properties of artemisinin and its derivatives have also been reported. This review has summarized the research and development of artemisinin and its derivatives as anticancer agents, which included both natural and synthetic monomers as well as their dimers. In addition, it highlights the antitumor effects of artemisinin and its derivatives after site-modification or after transformation to a nano-delivery system. Moreover, we have further explored their potential mechanisms of action and also discussed the clinical trials of ARTs used to treat cancer, which will facilitate in further development of novel anticancer drugs based on the scaffold of artemisinin.

Molecular Docking and Dynamics Simulation Revealed the Potential Inhibitory Activity of New Drugs against Human Topoisomerase I Receptor

Human Topoisomerase I (hTop1p) is a ubiquitous enzyme that relaxes supercoiled DNA through a conserved mechanism involving transient breakage, rotation, and binding. Htop1p is the molecular target of the chemotherapeutic drug camptothecin (CPT). It causes the hTop1p-DNA complex to slow down the binding process and clash with the replicative machinery during the S phase of the cell cycle, forcing cells to activate the apoptotic response. This gives hTop1p a central role in cancer therapy. Recently, two artesunic acid derivatives (compounds c6 and c7) have been proposed as promising inhibitors of hTop1p with possible antitumor activity. We used several computational approaches to obtain in silico confirmations of the experimental data and to form a comprehensive dynamic description of the ligand-receptor system. We performed molecular docking analyses to verify the ability of the two new derivatives to access the enzyme-DNA interface, and a classical molecular dynamics simulation was performed to assess the capacity of the two compounds to maintain a stable binding pose over time. Finally, we calculated the noncovalent interactions between the two new derivatives and the hTop1p receptor in order to propose a possible inhibitory mechanism like that adopted by CPT.

The current scenario on anticancer activity of artemisinin metal complexes, hybrids, and dimers

Cancer, the most significant cause of morbidity and mortality, has already posed a heavy burden on health care systems globally. In recent years, cancer treatment has made a significant breakthrough, but cancer cells inevitably acquire resistance, and the efficacy of the treatment is greatly reduced as the tumor progresses. To overcome the above issues, novel chemotherapeutics are needed urgently. Artemisinin and its derivatives-sesquiterpene lactone compounds possessing a unique peroxy bridge moiety-exhibit excellent safety and tolerability profiles. Mechanistically, artemisinin derivatives can promote cancer cell apoptosis, induce cell cycle arrest and autophagy, and inhibit cancer cell invasion and migration. Accordingly, artemisinin derivatives demonstrate promising anticancer efficacy both in vitro and in vivo, and even in clinical Phase I/II trials. The purpose of the present review article is to provide an emphasis on the current scenario (January 2017-January 2022) of artemisinin derivatives with potential anticancer activity, inclusive of artemisinin metal complexes, hybrids, and dimers. The structure-activity relationships and mechanisms of action are also discussed to facilitate the further rational design of more effective candidates.

Synthesis, Antiplasmodial, and Antileukemia Activity of Dihydroartemisinin–HDAC Inhibitor Hybrids as Multitarget Drugs

Artemisinin-based combination therapies (ACTs) are the gold standard for the treatment of malaria, but the efficacy is threatened by the development of parasite resistance. Histone deacetylase inhibitors (HDACis) are an emerging new class of potential antiplasmodial drugs. In this work, we present the design, synthesis, and biological evaluation of a mini library of dihydroartemisinin–HDACi hybrid molecules. The screening of the hybrid molecules for their activity against selected human HDAC isoforms, asexual blood stage P. falciparum parasites, and a panel of leukemia cell lines delivered important structure–activity relationships. All synthesized compounds demonstrated potent activity against the 3D7 and Dd2 line of P. falciparum with IC₅₀ values in the single-digit nanomolar range. Furthermore, the hybrid (α)-7c displayed improved activity against artemisinin-resistant parasites compared to dihydroartemisinin. The screening of the compounds against five cell lines from different leukemia entities revealed that all hydroxamate-based hybrids (7a–e) and the ortho-aminoanilide 8 exceeded the antiproliferative activity of dihydroartemisinin in four out of five cell lines. Taken together, this series of hybrid molecules represents an excellent starting point toward the development of antimalarial and antileukemia drug leads.

Lignin Nanoparticles Deliver Novel Thymine Biomimetic Photo-Adducts with Antimelanoma Activity

We report here the synthesis of novel thymine biomimetic photo-adducts bearing an alkane spacer between nucleobases and characterized by antimelanoma activity against two mutated cancer cell lines overexpressing human Topoisomerase 1 (TOP1), namely SKMEL28 and RPMI7951. Among them, Dewar Valence photo-adducts showed a selectivity index higher than the corresponding pyrimidine-(6-4)-pyrimidone and cyclobutane counterpart and were characterized by the highest affinity towards TOP1/DNA complex as evaluated by molecular docking analysis. The antimelanoma activity of novel photo-adducts was retained after loading into UV photo-protective lignin nanoparticles as stabilizing agent and efficient drug delivery system. Overall, these results support a combined antimelanoma and UV sunscreen strategy involving the use of photo-protective lignin nanoparticles for the controlled release of thymine dimers on the skin followed by their sacrificial transformation into photo-adducts and successive inhibition of melanoma and alert of cellular UV machinery repair pathways.

Artemisinin and Derivatives-Based Hybrid Compounds: Promising Therapeutics for the Treatment of Cancer and Malaria

Cancer and malaria are major health conditions around the world despite many strategies and therapeutics available for their treatment. The most used strategy for the treatment of these diseases is the administration of therapeutic drugs, which suffer from several shortcomings. Some of the pharmacological limitations associated with these drugs are multi-drug resistance, drug toxicity, poor biocompatibility and bioavailability, and poor water solubility. The currently ongoing preclinical studies have demonstrated that combination therapy is a potent approach that can overcome some of the aforementioned limitations. Artemisinin and its derivatives have been reported to exhibit potent efficacy as anticancer and antimalarial agents. This review reports hybrid compounds containing artemisinin scaffolds and their derivatives with promising therapeutic effects for the treatment of cancer and malaria.

Natural Product-Based Hybrids as Potential Candidates for the Treatment of Cancer: Focus on Curcumin and Resveratrol

One of the main current strategies for cancer treatment is represented by combination chemotherapy. More recently, this strategy shifted to the "hybrid strategy", namely the designing of a new molecular entity containing two or more biologically active molecules and having superior features compared with the individual components. Moreover, the term "hybrid" has further extended to innovative drug delivery systems based on biocompatible nanomaterials and able to deliver one or more drugs to specific tissues or cells. At the same time, there is an increased interest in plant-derived polyphenols used as antitumoral drugs. The present review reports the most recent and intriguing research advances in the development of hybrids based on the polyphenols curcumin and resveratrol, which are known to act as multifunctional agents. We focused on two issues that are particularly interesting for the innovative chemical strategy involved in their development. On one hand, the pharmacophoric groups of these compounds have been used for the synthesis of new hybrid molecules. On the other hand, these polyphenols have been introduced into hybrid nanomaterials based on gold nanoparticles, which have many potential applications for both drug delivery and theranostics in chemotherapy.

Stereoselective Access to Antimelanoma Agents by Hybridization and Dimerization of Dihydroartemisinin and Artesunic acid

A library of five hybrids and six dimers of dihydroartemisinin and artesunic acid has been synthetized in a stereo-controlled manner and evaluated for the anticancer activity against metastatic melanoma cell line (RPMI7951). Among novel derivatives, three artesunic acid dimers showed antimelanoma activity and cancer selectivity, being not toxic on normal human fibroblast (C3PV) cell line. Among the three dimers, the one bearing 4-hydroxybenzyl alcohol as a spacer showed no cytotoxic effect (CC50 >300 μM) and high antimelanoma activity (IC50 =0.05 μM), which was two orders of magnitude higher than that of parent artesunic acid, and of the same order of commercial drug paclitaxel. In addition, this dimer showed cancer-type selectivity towards melanoma compared to prostate (PC3) and breast (MDA-MB-231) tumors. The occurrence of a radical mechanism was hypothesized by DFO and EPR analyses. Qualitative structure activity relationships highlighted the role of artesunic acid scaffold in the control of toxicity and antimelanoma activity.

Antimalarial and anticancer properties of artesunate and other artemisinins: current development

This review provides a recent perspective of artesunate and other artemisinins as antimalarial drugs and their uses in cancer therapy. Artesunate is an artemisinin derivative. Artemisinin is extracted from the plant Artemisia annua. Artemisinin and its derivatives have been the most useful drug for malarial treatment in human history. The artesunate has an advantage of a hydrophilic group over other artemisinins which makes it a more potent drug. On the industrial scale, artemisinins are synthesized in semisynthetic ways. The 1,2,4-endoperoxide bridge of artemisinins is responsible for the drug's antimalarial activity. There is the emergence of artemisinin resistance on Plasmodium falciparum and pieces of evidence suggest that it is mainly due to the mutation at Kelch13 protein of P. falciparum. Clinical trial data show that the artesunate is more favorable than quinine and other artemisinins to treat patients with severe malaria. Pieces of evidence indicate that artemisinins can be developed as anticancer drugs. The mechanism of actions on how artemisinins act as an anticancer drug involves oxidative stress, DNA damage and repair, and various types of cell deaths.

GRAPHIC ABSTRACT

Dihydroartemisinin loaded layered double hydroxide nanocomposites for tumor specific photothermal-chemodynamic therapy

With the inspiration to develop new cancer nanotherapeutics by repurposing old drugs, in the current study, a novel two dimensional nanomedicine namely Mn doped, dihydroartemisinin (DHA) loaded layered double hydroxide (MnMgFe-LDH/DHA) with peroxide self-supplying properties for enhanced photothermal-chemodynamic therapy was proposed. Such nanostructures could be synthesized by a simple coprecipitation method, and the as-prepared MnMgFe-LDH/DHA exhibits excellent photothermal properties with a photothermal conversion efficiency up to 10.7%. Besides, the in situ reaction between the released DHA and Fe2+/Mn2+ produced by the degradation of LDH can lead to a burst of intracellular reactive oxygen species (ROS) by Fenton-like reactions. Furthermore, the in vivo experiments demonstrate that MnMgFe-LDH/DHA exhibits a remarkable chemodynamic/photothermal therapy (CDT/PTT) synergistic effect on tumor treatment with negligible damage to normal tissues. Finally, this research provides a smart strategy to construct a DHA repurposing nanomedicine for tumor specific treatment.

4-Aminosalicylic Acid-based Hybrid Compounds: Synthesis and In vitro Antiplasmodial Evaluation

Background:

Malaria is a deadly and infectious disease responsible for millions of death worldwide, mostly in the African region. The malaria parasite has developed resistance to the currently used antimalarial drugs, and it has urged researchers to develop new strategies to overcome this challenge by designing different classes of antimalarials.

Objectives:

A class of hybrid compounds containing 4-aminosalicylic acid moiety was prepared via esterification and amidation reactions and characterized using FTIR, NMR and LC-MS. In vitro antiplasmodial evaluation was performed against the asexual NF54 strain of P. falciparum parasites.

Methods:

In this research, known 4-aminoquinoline derivatives were hybridized with 4- aminosalicylic acid to afford hybrid compounds via esterification and amidation reactions. 4- aminosalicylic acid, a dihydrofolate compound inhibits DNA synthesis in the folate pathway and is a potential pharmacophore for the development of antimalarials.

Results:

The LC-MS, FTIR, and NMR analysis confirmed the successful synthesis of the compounds. The compounds were obtained in yields in the range of 63-80%. The hybrid compounds displayed significant antimalarial activity when compared to 4-aminosalicylic acid, which exhibited poor antimalarial activity. The IC50 value of the most potent hybrid compound, 9 was 9.54±0.57 nm.

Conclusion:

4-aminosalicylic has different functionalities, which can be used for hybridization with a wide range of compounds. It is a potential pharmacophore that can be utilized for the design of potent antimalarial drugs. It was found to be a good potentiating agent when hybridized with 4- aminoquinoline derivatives suggesting that they can be utilized for the synthesis of a new class of antimalarials.

Exploration of artemisinin derivatives and synthetic peroxides in antimalarial drug discovery research

Malaria is a life-threatening infectious disease caused by protozoal parasites belonging to the genus Plasmodium. It caused an estimated 405,000 deaths and 228 million malaria cases globally in 2018 as per the World Malaria Report released by World Health Organization (WHO) in 2019. Artemisinin (ART), a "Nobel medicine" and its derivatives have proven potential application in antimalarial drug discovery programs. In this review, antimalarial activity of the most active artemisinin derivatives modified at C-10/C-11/C-16/C-6 positions and synthetic peroxides (endoperoxides, 1,2,4-trioxolanes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes) are systematically summarized. The developmental trend of ART derivatives, and cyclic peroxides along with their antimalarial activity and how the activity is affected by structural variations on different sites of the compounds are discussed. This compilation would be very useful towards scaffold hopping aimed at avoiding the unnecessary complexity in cyclic peroxides, and ultimately act as a handy resource for the development of potential chemotherapeutics against Plasmodium species.

Strain-release enabled [3 + 2] annulation of 3-aminooxetanes with simple CN bonds: facile synthesis of imidazolidines

An unprecedented [3+2] annulation of readily available 1,3,5-triazinanes and 3-aminooxetanes is accomplished for the first time, enabling the convenient synthesis of a range of structurally diverse 4-hydroxymethyl imidazolidines.

Artemisinin Derivatives with Antimelanoma Activity Show Inhibitory Effect against Human DNA Topoisomerase 1

Artesunic acid and artemisinin are natural substances with promiscuous anticancer activity against different types of cancer cell lines. The mechanism of action of these compounds is associated with the formation of reactive radical species by cleavage of the sesquiterpene pharmacophore endoperoxide bridge. Here we suggested topoisomerase 1 as a possible molecular target for the improvement of the anticancer activity of these compounds. In this context, we report that novel hybrid and dimer derivatives of artesunic acid and artemisinin, bearing camptothecin and SN38 as side-chain biological effectors, can inhibit growth of yeast cells overexpressing human topoisomerase 1 and its enzymatic activity in vitro. These derivatives showed also anticancer activity in melanoma cell lines higher than camptothecin and paclitaxel. In silico molecular docking calculations highlighted a common binding mode for the novel derivatives, with the sesquiterpene lactone scaffold being located near the traditional recognition site for camptothecin, while the bioactive side-chain effector laid in the camptothecin cleft.